Synergistic blends of cellulase-free xanthan gum and cellulosics

ABSTRACT

This invention relates to a blend of cellulase-free xanthan gum with a number of cellulosics, including carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropylmethyl cellulose. At 1:1 weight ratio, these blends show surprising viscosities when tested in aqueous solutions of 1%, 0.5%, 0.25% and 0.1% total gum concentration. The blends have utility in any application where cellulosics are used as thickeners, such as industrial or food applications, e.g., toothpaste, or drink mix formulations.

RELATIONSHIP TO THE PRIOR ART

Different gum blends are widely known and used. It has been found that the described blends show unusual synergism and are not suggested by the prior art. Generally cellulosics were incompatible with xanthan gum, due to presence in the latter of various cellulase enzymes. However, cellulosics, although widely used, suffer, to varying degrees in different applications from salt incompatibility, instability to heat, limited shelf life, instability to pH changes, and unpleasant or undesirable mouth-feel in certain compositions such as toothpaste.

However, if cellulosics were mixed with many other gums in order to improve these characteristics, the final viscosity was usually detrimentally affected.

It has now been found that cellulosics, including carboxymethylcellulose, hydroxyethylcellulose, or hydroxypropylmethylcellulose, can be mixed with cellulase-free xanthan gum. Not only are the desirable properties of the cellulosics retained and the undesirable properties of cellulosics minimized, but the resulting viscosities of the solutions prepared from these blends is surprisingly and unexpectedly higher than that predicted from measurements of either component alone.

The synergistic effect can be demonstrated in synthetic tap water (STW) on 1:1 (weight basis) blends, thereby keeping the good qualities of cellulosics with a 50% dilution, and the good qualities of xanthan gum at 50% dilution, while maintaining and even increasing viscosity of solutions of these 1:1 blends. The synergistic effect in viscosity can be demonstrated at 1%, 0.5%, 0.25% and 0.1% concentration levels in Synthetic Tap Water (STW); the synergism is not as pronounced in deionized water.

THE MATERIALS USED

The cellulosics useful in this invention are all the commercially available forms of cellulosics, including carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, or microcrystalline cellulose. Other commonly known or used cellulosics can be also employed.

The cellulase-free xanthan gum can be any of a number of grades available. One form is produced by treating xanthan gum beer with alkali metal hypochlorite, pH 6 to 7, at concentration levels of 0.08-0.1% by weight and about 30° C. for 6-8 hours, followed by heating to 85°-95° C. for several minutes, then recovering, by precipitating the cellulase-free beer, and by drying and milling the presscake. Other methods include treatment of xanthan gum beer with mercury compounds, treatment of xanthan gum beer presscakes with propylene oxide, and heating xanthan gum beer that has been adjusted to high pH to about 90° C. followed by cooling and neutralization.

FORMING THE BLEND

The two gums are dry blended, at about a 1:1 weight ratio, by rolling or any other such technique. Another method involves adding the desired cellulosic to cellulase-free xanthan gum beer, and then recovering the blend using the normal recovery steps for xanthan gum alone.

USING THE BLEND

These blends can be employed in any formulation where cellulosics are used, such as toothpastes or drink mixes. A formulation for toothpaste using this blend follows:

    ______________________________________                                         TOOTHPASTE                                                                                         %      gm                                                  ______________________________________                                         Sorbitol              12.5     500                                             Glycerol              12.5     500                                             DCPD (dicalcium phosphate dihydrate)                                                                 45.0     1800                                            Sodium lauryl sulfate 1.5      60                                              Methylparaben         0.15     6                                               Titanium dioxide      0.75     30                                              Saccharin             0.15     6                                               Flavor                1.0      40                                              Color                 0.02     0.8                                             Water                 25.43    1017.2                                          Carboxymethylcellulose                                                                               0.5      40                                              Xanthan gum, cellulase free                                                                          0.5      40                                                                    100.0%   4000 g.                                         ______________________________________                                    

The final toothpaste was completely suitable.

DETERMINATION OF SYNERGISM

Data was determined for 1%, 0.5%, 0.25%, and 0.1% concentration of a 1:1 blend of the indicated gums. Two methods were used to calculate theoretical expected values, one the log-plot (see U.S. Pat. No. 4,169,818 for reference to this method) the other, the sum of 1/2 viscosities. Values were also calculated by mathematical average, but these were not considered as reliable and are not included. The data is summarized in Tables I, II, III and IV.

                                      TABLE I                                      __________________________________________________________________________     % Synergism of Cellulase-Free XG with Cellulosics in STW.sup.1 : 1.0%          Total Solids                                                                             Gum Viscosity   Blend Viscosity (1:1)                                          0.5%    1.0%    Viscosity A                                                                           Viscosity B                                   Sample    Viscosity/STW                                                                          Viscosity/STW                                                                          Experimental                                                                          Theoretical Value.sup.2                                                                  % Synergism.sup.3                   __________________________________________________________________________     Carboxy-  92.5    626     1150   (a) 995   + 16                                methylcell-                      (b) 622.5 + 85                                ulose, 7HOF                                                                    Hydroxy-  57.5    550     1220   (a) 935   + 30                                ethylcell-                       (b) 587.5 +108                                ulose, QP4400                                                                  Hydroxy-  20.5    115     1000   (a) 500   +100                                propylmethyl                     (b) 550.5 + 82                                cellulose,                                                                     Methocel, 90HG                                                                 Cellulase-                                                                               530     1586    --     --        --                                  free xanthan                                                                   gum (Produced by                                                               hypochlorite treat-                                                            ment)                                                                          __________________________________________________________________________      .sup.1 synthetic tap water  1000 ppm NaCl & 143 ppm CaCl.sub.2 . 2H.sub.2      O in D.I. water.                                                               .sup.2 (a) calculated from logplot of 1.0% viscosities.                        (b) calculated from sum of 0.5% viscosities.                                   ##STR1##                                                                 

                                      TABLE II                                     __________________________________________________________________________     % Synergism of Cellulase-Free XG with Cellulosics in STW.sup.1 : 0.5%          Total Solids                                                                             Gum Viscosity   Blend Viscosity (1:1)                                          0.25%   0.5%    Viscosity A                                                                           Viscosity B                                   Sample    Viscosity/STW                                                                          Viscosity/STW                                                                          Experimental                                                                          Theoretical Value.sup.2                                                                  % Synergism.sup.3                   __________________________________________________________________________     Carboxy-  19.5    84.5    247.5  (a) 198   + 25                                methylcell-                       (b) 154.5                                                                               + 60                                ulose,                                                                         7HOF                                                                           Hydroxy-  10      40      230    (a) 136   + 69                                ethylcell-                       (b) 142   + 59                                ulose,                                                                         QP4400                                                                         Hydroxy-  7       20.5    200    (a)  98   +104                                propylmethyl                     (b) 142   + 41                                cellulose                                                                      Methocel, 90HG                                                                 Cellulase-                                                                               135     466.3   --     --        --                                  free xanthan                                                                   gum (produced                                                                  by hypochlorite                                                                treatment)                                                                     __________________________________________________________________________      .sup.1 Synthetic tap water  1000 ppm NaCl and 143 ppm CaCl.sub.2 .             2H.sub.2 O in D.I. water.                                                      .sup.2 (a) calculated from logplot of 0.5% viscosities                         (b) calculated from sum of 0.25% viscosities.                                  ##STR2##                                                                 

                                      TABLE III                                    __________________________________________________________________________     % Synergism of Cellulase-Free XG with Cellulosics in STW.sup.1 : 0.25%         Total Solids                                                                             Gum Viscosity   Blend Viscosity (1:1)                                          0.125%  0.25%   Viscosity A                                                                           Viscosity B                                   Sample    Viscosity/STW                                                                          Viscosity/STW                                                                          Experimental                                                                          Theoretical Value.sup.2                                                                  % Synergism.sup.3                   __________________________________________________________________________     Carboxy-  7.8     19.5    56.5   (a) 52    + 9                                 methylcell-                       (b) 48.4 +17                                 ulose, 7HOF                                                                    Hydroxy-  3.25    10      50     (a) 37    +35                                 ethylcell-                         (b) 43.85                                                                              +14                                 ulose, QP4400                                                                  Hydroxy-  3.8     7       44.5   (a) 31    +44                                 propylmethyl                      (b) 44.4  +0.2                               cellulose,                                                                     Methocel 90HG                                                                  Cellulase-                                                                               40.6    135     --     --        --                                  free xanthan                                                                   gum (Produced by                                                               hypochlorite treat-                                                            ment)                                                                          __________________________________________________________________________      .sup.1 Synthetic tap water  1000 ppm NaCl and 143 ppm CaCl.sub.2 .             2H.sub.2 O in D.I. water.                                                      .sup.2 (a) calculated from logplot of 0.25% viscosities.                       (b) calculated from sum of 0.125% viscosities.                                 ##STR3##                                                                 

                                      TABLE IV                                     __________________________________________________________________________     % Synergism of Cellulase-Free XG with Cellulosics in STW.sup.1 : 0.1%          Total Solids                                                                             Gum Viscosity   Blend Viscosity (1:1)                                          0.05%   0.1%    Viscosity A                                                                           Viscosity B                                   Sample    Viscosity/STW                                                                          Viscosity/STW                                                                          Experimental                                                                          Theoretical Value.sup.2                                                                  % Synergism.sup.3                   __________________________________________________________________________     Carboxy-  3.5     6.5     15.0   (a) 14.3  + 5                                 methylcell-                      (b) 12.5  +20                                 ulose, 7HOF                                                                    Hydroxy-  2.5     3.9     12.5   (a) 11.0  +14                                 ethylcell-                       (b) 11.5  + 9                                 ulose, QP4400                                                                  Hydroxy-  4.0     6.0     16.0   (a) 13.6  +18                                 propylmethyl                     (b) 13.0  +23                                 cellulose,                                                                     Methocel, 90HG                                                                 Cellulase-                                                                               9.0     31.5    --     --        --                                  free xanthan                                                                   gum (Produced by                                                               hypochlorite treat-                                                            ment)                                                                          __________________________________________________________________________      .sup.1 Synthetic tap water  1000 ppm NaCl and 143 ppm CaCl.sub.2 .             2H.sub.2 O in D.I. water.                                                      .sup.2 (a) Calculated from logplot of 0.1% viscosities.                        (b) Calculated from sum of 0.05% viscosities.                                  ##STR4##                                                                 

Other data were obtained by dissolving the dry gum powder blends (1:1) in 1% KCl and viscosities (1% total solids) measured using a Brookfield LVF viscometer, spindle No. 3 at 60 rpm, and are shown in Table V.

                                      TABLE V                                      __________________________________________________________________________     % Synergism of Cellulase-Free XG with Cellulosics in 1% KCl: 1% Total          Solids                                                                                  Gum Viscosity                                                                          Blend Viscosity (1:1)                                                  1%      Viscosity A                                                                            Viscosity B                                           Sample   Viscosity/KCl                                                                          Experimental                                                                           Theoretical Value.sup.1                                                                  % Synergism.sup.2                           __________________________________________________________________________     Carboxymethyl-                                                                          860     1180    1150       3                                          cellulose,                                                                     7HOF                                                                           Hydroxyethyl-                                                                           310     820     680       21                                          cellulose                                                                      Hydroxypropyl-                                                                          180     780     520       50                                          methylcellulose                                                                Methocel 90HG                                                                  Cellulase-free                                                                          1500    --      --        --                                          xanthan gum                                                                    __________________________________________________________________________      .sup.1 Calculated from log plots of 1.0% viscosities.                          ##STR5##                                                                  

What is claimed is:
 1. A 1:1 (weight basis) blend composition of cellulase-free xanthan gum and either carboxymethylcellulose, hydroxyethylcellulose or hydroxypropylmethylcellulose.
 2. The composition of claim 1 in which carboxymethylcellulose is used.
 3. The composition of claim 1 in which hydroxyethylcellulose is used.
 4. The composition of claim 1 in which hydroxypropylmethylcellulose is used. 